The great filter now is being not able to stop burning fossil fuels while our greenhouse effect grows and industrial civilisation growth causes another global mass extinction including our own.

During past global heating events, a long term rise in CO2, heat and extinctions, and stagnant oceans deplete the species that maintain atmosphere oxygen levels high enough for us high metabolic rate large creatures.

We are in a civilisation growth trap. The rocket equation, extreme interstellar distances and need for radiation shielding should tell us that no species like ours is likely to be able to colonise a galaxy, despite all the sci-fi.

If we are to survive this bottleneck and maintain a science-techno ability, then bio-engineering, geo-engineering, better international cooperation, and becoming less delusional are our current frontier challenges.